Autologous atrial appendage tissue has not been pursued as a cell source for ventricular myocardial infarct repair although it is the only expendable portion of the human heart. To date, the use of adult cardiomyocytes in tissue engineering has been limited by their rapid apoptosis in vitro and in vivo. In preliminary work, however, it was demonstrated that ex vivo induction of heme oxygenase-1 (HO-1), a mediator of late pre- conditioning, could increase adult cardiomyocyte survival by 140% at 14 days following in vivo implantation. Furthermore, almost 50% of treated patches began spontaneous, synchronized contraction by 14 days, unlike patches implanted directly without culture, patches cultured without HO-1 induction, or patches cultured with specific HO-1 inhibitors. Implanted as three-dimensional flattened patches, myocytes in patches with HO-1 upregulation spontaneously remodeled around vascular spaces to form pumping chambers filled with non- clotting blood. These findings suggest that adult cardiomyocytes may have more plasticity than previously thought, and that, with optimization, might be suitable as an autologous cell source for infarct repair and cardiac tissue engineering. Experiments will investigate clinically relevant novel strategies designed to meet four current challenges to the use of autologous adult cardiomyocytes: improving myocyte tolerance to ischemia; integrating patches with host vasculature; reducing fibrosis; and maximizing function after implantation on the heart. To overcome myocyte apoptosis, transcriptional activators of HO-1 will be delivered both ex vivo and intravenously, testing a new permeabilizing agent as a means to improve drug delivery to the central cells of three-dimensional tissue grafts. Hydrogels with timed release of bFGF will be applied with mobilized omental pedicles to foster integration with host vasculature and create a high volume extracardiac blood source to support the patch. Local AAV gene delivery of HO-1 to the patch will be used to explore the long-term matrix modulatory effects of HO-1 on interstitial fibrosis. Finally, the consequences of patch myofiber alignment and ischemic re-programming of contractile proteins on patch biomechanics and ventricular function will be assessed. A unique aspect of the project is the opportunity to use human atrial tissue from cardiac surgical patients to replace mouse tissue as a donor source in parallel experiments. Thus, experimental strategies will be tested in tissue from the very patient population likely to benefit from this new technology in the future. This project is a multidisciplinary effort between surgeons, bioengineers, and matrix biologists, working together toward an important therapeutic endpoint with expected early clinical applicability. Relevance to public health: Heart disease is the leading cause of death in the United States. After a heart attack, heart muscle mass is irreversibly lost, often leading to heart failure. Current methods under investigation to replace lost muscle propose using embryonic stem cells or cell types that have not been shown to transform into heart muscle. This project investigates the novel, but likely possibility that the patient's own expendable heart muscle cells from the atrial chamber could be modified to allow them to survive transplantation onto the injured ventricle to prevent and treat heart failure. [unreadable] [unreadable] [unreadable]